Faraday Cages
A Faraday cage is a metallic enclosure that prevents the entry of escape of an electromagnetic field (EM field). An ideal Faraday cage would consist of an unbroken, perfectly conducting shell.
To protect your Wi-Fi network from surrounding buildings. The most obvious way to do this would be to secure the devices on your network using the wireless security protocol of choice. A very effective, but more extreme, way to do this would be to secure the building itself by making it act as a Faraday cage, shielding the radio frequency waves used by Wi-Fi.
Making a large building into a Faraday cage involves encasing the building in a thin layer of conductive material or metal mesh. In physics, a Faraday cage or Faraday shield – named for the British physicist Michael Faraday, who discovered the phenomenon in the 19th century and built the first iteration in 1836 – is an ingenious application of Gauss’ law. Gauss’ Law establishes the relation between electric flux flowing out of a closed surface and the electrical charge enclosed inside the surface. Basically, in a hollow object that can conduct electricity, such as an aluminum sphere, charge will ideally distribute itself evenly over the surface of the sphere, and there won’t be an electric field inside the sphere. This has the effect of blocking EMFs (electromagnetic fields) and shielding radio frequency waves.
Faraday cages are far more common entities that you might realize. For instance, cars and airplanes can act like Faraday cages. That’s why a lightning bolt striking an airplane is unlikely to take the airplane down; the aircraft will distribute the electric charge over its entire surface, protecting what’s inside. If you were in a car, and the car got struck by lighting, it is not in fact the rubber tires that would save your life. What actually happens is by being enclosed by the car’s cabin, the lightning travels around you, though the conductive frame of the car. This is because the car forms a Faraday Cage. You’ve probably experienced the phenomenon in even more mundane circumstances like losing your cell-phone coverage inside an office building, or radio reception as you pass thorugh a tunnel. And you are like to “assemble” a Faraday cage on a regular basis: The metal screen built into the glass of your microwave oven the act as a Faraday cage when the door is closed.
But constructing a functional, building-size Faraday cage might be another matter. Not only would it be costly, but other equipment is likely to be hindered by the effect. For instance, cell phones will get poor reception or most likely not work at all in a building tricked out to be Faraday cage. For a small space, though, such a structure might make perfect sense. Other expensive and goofy techniques to achieve similar ends, such as “Wi-Fi-proof wallpaper” and “Wi-Fi paint” with metallic ingredients, have been rolled out over the past few years, but unless you live in a cave, you’d probably also need to replace your windows with special radio-absorbing glass.
Small installations of RF shielding don’t have to be expensive, and the basic concept of a Faraday cage can be extended to all kinds of small everyday objects. Leather wallets sandwiched with a conductive RF-shielding layer can prevent RFID scanners from reading personal information implanted in everything from RFID-enabled access control cards to some credit cards; they’re widely available for as little as $15.
For those favoring a more DIY route, several websites have information on how to make an RFID-blocking wallet with duct tape and aluminum foil. The US passports are now set to include RFID chips, and future editions of the US currency might be RFID-enabled too. Expect further expansion of the burgeoning market for RFID-blocking wallets, passport holders and other paraphernalia for the paranoid and/or privacy savvy consumer, from companies such as Envelope and DIFRWear, which sports the motto “Faraday caged apparel.”
A Faraday cage is a metallic enclosure that prevents the entry of escape of an electromagnetic field (EM field). An ideal Faraday cage would consist of an unbroken, perfectly conducting shell.
To protect your Wi-Fi network from surrounding buildings. The most obvious way to do this would be to secure the devices on your network using the wireless security protocol of choice. A very effective, but more extreme, way to do this would be to secure the building itself by making it act as a Faraday cage, shielding the radio frequency waves used by Wi-Fi.
Making a large building into a Faraday cage involves encasing the building in a thin layer of conductive material or metal mesh. In physics, a Faraday cage or Faraday shield – named for the British physicist Michael Faraday, who discovered the phenomenon in the 19th century and built the first iteration in 1836 – is an ingenious application of Gauss’ law. Gauss’ Law establishes the relation between electric flux flowing out of a closed surface and the electrical charge enclosed inside the surface. Basically, in a hollow object that can conduct electricity, such as an aluminum sphere, charge will ideally distribute itself evenly over the surface of the sphere, and there won’t be an electric field inside the sphere. This has the effect of blocking EMFs (electromagnetic fields) and shielding radio frequency waves.
Faraday cages are far more common entities that you might realize. For instance, cars and airplanes can act like Faraday cages. That’s why a lightning bolt striking an airplane is unlikely to take the airplane down; the aircraft will distribute the electric charge over its entire surface, protecting what’s inside. If you were in a car, and the car got struck by lighting, it is not in fact the rubber tires that would save your life. What actually happens is by being enclosed by the car’s cabin, the lightning travels around you, though the conductive frame of the car. This is because the car forms a Faraday Cage. You’ve probably experienced the phenomenon in even more mundane circumstances like losing your cell-phone coverage inside an office building, or radio reception as you pass thorugh a tunnel. And you are like to “assemble” a Faraday cage on a regular basis: The metal screen built into the glass of your microwave oven the act as a Faraday cage when the door is closed.
But constructing a functional, building-size Faraday cage might be another matter. Not only would it be costly, but other equipment is likely to be hindered by the effect. For instance, cell phones will get poor reception or most likely not work at all in a building tricked out to be Faraday cage. For a small space, though, such a structure might make perfect sense. Other expensive and goofy techniques to achieve similar ends, such as “Wi-Fi-proof wallpaper” and “Wi-Fi paint” with metallic ingredients, have been rolled out over the past few years, but unless you live in a cave, you’d probably also need to replace your windows with special radio-absorbing glass.
Small installations of RF shielding don’t have to be expensive, and the basic concept of a Faraday cage can be extended to all kinds of small everyday objects. Leather wallets sandwiched with a conductive RF-shielding layer can prevent RFID scanners from reading personal information implanted in everything from RFID-enabled access control cards to some credit cards; they’re widely available for as little as $15.
For those favoring a more DIY route, several websites have information on how to make an RFID-blocking wallet with duct tape and aluminum foil. The US passports are now set to include RFID chips, and future editions of the US currency might be RFID-enabled too. Expect further expansion of the burgeoning market for RFID-blocking wallets, passport holders and other paraphernalia for the paranoid and/or privacy savvy consumer, from companies such as Envelope and DIFRWear, which sports the motto “Faraday caged apparel.”
